DovBear decries the separation between Jews caused by stringencies, particularly in kashruth, comparing it with the Temple-era when divisions were created between conscientious kohanim and `amei ha-'aretz over similar matters.
My thinking is that problem is denominationalism in Judaism. While most people then were not Perushim and were not Tzedokim, they were the `am. It was not realistic to see them as part of another interpretation of Judaism, as opposed to a simple, uneducated class. In a sense, in pre-war eastern Europe this existed a little bit as well, even though obviously there were denominations and ideological movements. But there was still a large class of people who weren't knowledgeable at all and maybe who weren't even close to meticulously observant, but who co-existed alongside those who were both. They too were viewed as simply the `am and not Zionists or Bundists or Maskilim or Hassidim.
Unfortunately this is not true today because most Jews seem to be identified with a label of some sorts, as well as the fact that most Jews are either quite removed from tradition or are wedded to other traditions.
DB points out that "This is one advantage the catholics have over us. They still have the sence of the am - even for people who are knowledgeable, and dissenters, and attached to other traditions. No one doubts that they are "real" catholics."
Perhaps that is overly idealized, and I wouldn't mind if a Catholic reader weighed in (are you there? :) ), but there's something to the idea, even if it isn't true on the ground from the perspective of Catholics. Denominationalism stinks, even if some of our own denominationalists claim on principle that there are no denominations in Judaism! The trouble is that this principle relies on a claim, that only our own interpretation is entitled to be called Judaism, which in itself is seen as divisive (rightly or not). Note that in large measure this is an Ashkenazic problem; the Sepharadim and `edot ha-mizrah also never split and have much more of a sense of `am, as far as I can tell.
By the way, Martin Buber believed that `am was etymologically derived from `im, which means 'with.' Therefore 'am connotes unity and attachment. It's a nice midrash, even if it might not be linguistically correct.